"I get bored easily and I look for ways for me to be creative," the actor, singer, writer and voice-over artist tells PEOPLE. "I'm always looking for things that are fun and new and exciting."

McCartney, 26, is known for his 2003 hit "Beautiful Soul" and his work on the television shows Army Wives, Greek and Summerland. But did you know he got his start in 1998 on All My Children? Or that he co-wrote Leona Lewis's hit "Bleeding Love"? And what about his time spent voicing video game and cartoon characters including Theodore in the popular Alvin and the Chipmunk films?

"Once in a while, I'll get a 40-year-old gamer and he'll say, 'I love that video game you did for the Japanese. I've spent 80 hours playing it,' " says McCartney. "And in the next room there'll be a 15-year-old girl who is a fan."

He may only play a college student on TV, but actor Scott Michael Foster admits he put on the dreaded "freshman 15" during his first season starring on the ABC Family show Greek.

"I was so happy about having a job and not having to worry about paying the food bill, I ate anything on set," says Foster, 24. "Fried chicken, mashed potatoes, you name it. I got sucked into craft services and, yes, it was just like college!"

The 6'3" actor, who plays Cappie on the hit show, quickly reached 200 lbs. Around the same time, he also found out he was allergic to gluten. "It runs in my family," says Foster, whose symptoms included a bloated stomach and extremely dry skin on his hands. "It just got worse and worse and I was like, 'This can't be normal!' "